In an internal combustion engine, a fuel pump supplies each cylinder of the engine with fuel at high pressure by means of dedicated fuel injector. Typically, the fuel injector is fitted in a bore provided in a cylinder head, and a fuel lance is used to provide a fluid connection between the injector and the supply duct coming from the fuel pump.
This type of assembly is known from EP0974749 and is shown in FIG. 1. A fuel lance 10 comprises a tubular member 22, with a first end 46 which is designed to cooperate with the seat 16 of an injector 12, and a second end 48 which is formed in order to define a frusto-conical seat 24. A securing nut 26 is partially inside an end of a bore 20, with the securing nut 26 comprising an inner end region 28 which is designed to cooperate with the seat 24.
The securing nut 26 comprises an outer threaded region 30. The thread 30 is designed to cooperate with threads of screws formed in the end 48 of the bore 20. In use, the securing nut 26 is secured inside the end 48 of the bore 20. The inner end 28 of the securing nut 26 cooperates with the seat 24 of the tubular element 22, by applying a compression force against the tubular member 22 in order to form a seal, both between the tubular member 22 and the seat 16 of the injector 12, and between the nut 26 and the tubular member 22.
The tubular member 22 and the securing nut 26 each comprise passages which extend axially, and together define a flow path. The fuel can flow through the fuel lance 10 to the supply passage 18 of the injector 12 from a high-pressure fuel hose 34 which is secured on the securing nut 26 by means of a standard securing tube 36. As illustrated in FIG. 1, the bore in the securing nut 26 extends axially, and comprises a region with a larger diameter which receives a filter element with a slot 38 designed to filter the undesirable particles which come from the flow of fuel towards the injector 12.
The head 14 comprises a passage 42 which communicates with the bore 20, with the passage 42 allowing the low-pressure fuel to flow from the injector 12 through the bore 20, towards a low-pressure fuel tank (not described). The securing nut 26 comprises a proximal recess in the threaded region 30, which positions an annular sealing element 32, designed to form a seal against the fluids, between the securing nut 26 and the wall of the head 14 which defines the bore 20.
A problem which exists concerning the high-pressure fuel supply device is that the sealing between the fuel lance and the injection nozzle requires tightening of a securing screw in the head, and transfer of the load of the screw to the fuel lance. This mechanism also gives rise to rotation of the parts, and generation of undesirable particles in the form of debris, which could lead to contamination of the fuel and wear of the components.
In order to solve this problem, the invention consists of an anti-rotation device for the fuel lance, in order to prevent its rotation inside the head, and thus to transmit the required load better.